A corresponding drill is known from DE 202 11 589 U1.
The aforesaid prior art, from which the present invention is starting out, provides that the width of the circumferential guiding margins, which correspond to the circumference of the secondary webs, increases in the axial direction starting from the drill point. According to an embodiment of this known drill, it is further provided that the cutting edge of the secondary cutting edge is recessed in the axial direction with respect to the corresponding cutting corner of the main cutting edge, which is ahead of the secondary cutting edge in the working direction.
With such a drill, a bore is thus first produced with the main cutting edge, wall the wall or fringe is still subjected to a post-processing by the subsequent secondary cutting edge. In this way, burrs and fractions of the borehole edge produced by the leading main cutting edge or the borehole wall are to be eliminated by means of the trailing edge. Depending on the type of laminates processed or the materials from which the laminates are composed, in particular when using laminates which contain a considerable amount of hard fiber components, the main cutting edges wear very rapidly so that the service life of these conventional drills within which they are producing a well-defined bore diameter, and smooth wellbore edges without overlying fiber residues or burrs is relatively short.
A disadvantage of the known drills is, therefore, that, in a fresh condition they can still produce relatively clean drill holes and through-holes in laminate material, however, the main cutting edges wear out relatively quickly, especially in the area of the cutting corners, and thus the material to be drilled is no longer cut in a smooth manner, so that the secondary cutting edge, which subsequently operates on the same diameter, must also machine a very uneven bore fringe, which then only succeeds in an insufficient manner.